Yeah but it looks like Typecast is just another “Typekit” font service, right?
Font-Combinator is just a free tool that shows you all of the google fonts so you can just see what might work together then just go grab them. So if you use google fonts only, it might be a good tool to mess around in.
No, because Typecast doesn’t offer any licensing to the user for font usage and it doesn’t limit you like Font Combinator. Typecast allows you to select from multiple distributors and test in layouts that you choose.